LaTeX.org

I would like to get the empty square root symbol.

Both and produce check mark which starts of the square root
but are missing horizontal line which follows.

Under cygwin, the following latex code
\documentclass{article}

\begin{document}

One of the most important inequalities in calculus is
\[
0 < |x−a| < \delta
\]
where $\delta$ is a positive real number.

\end{document}

when run through latex, dvips and gv commands or pdflatex command
is missing ...